TypeError (can't cast Enumerator to string): - Ruby on Rails

Hi,

When I am trying to upload a file through the url -
http://0.0.0.0:3000/upload/get . I am getting an error as

Started POST “/upload/save” for 127.0.0.1 at 2014-05-27 01:29:29 +0530
Processing by UploadController#save as HTML
Parameters: {“utf8”=>“✓”,
“authenticity_token”=>“khU59z0DsXoVyHeu4XNaUb7TEpSWZ9id4dJTbVu6efU=”,
“picture”=>{“comment”=>“dfgjk”,
“uploaded_picture”=>#<ActionDispatch::Http::UploadedFile:0xa939838
@tempfile=#Tempfile:/tmp/RackMultipart20140527-11473-10esj62,
@original_filename=“sfnzf.png”, @content_type=“image/png”,
@headers=“Content-
Disposition: form-data; name="picture[uploaded_picture]";
filename="sfnzf.png"\r\nContent-Type: image/png\r\n”>},
“commit”=>“Upload
file”}
(0.2ms) begin transaction
Binary data inserted for string type on column content_type
(0.1ms) rollback transaction
Completed 500 Internal Server Error in 5ms

TypeError (can’t cast Enumerator to string):
app/controllers/upload_controller.rb:8:in `save’

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I am reading a book and trying out stuffs and got stuck here. My little
tutorial is uploaded here -
https://github.com/aruprakshit/chap_21_agile_rails .

Please help me to understand what wrong am I doing here.

Regards,
Arup R.